Control Flow Analysis¶

Control flow analysis is a static analysis technique that examines the possible execution paths through a program. It builds upon the control flow graph to reason about which statements may be reached, which branches may be taken, and which code may be unreachable.

Applications include:

Dead code detection: identifying statements that can never be executed
Reachability analysis: determining whether a particular point in the code can be reached
Exception flow: tracing all paths through try/catch/finally blocks
Return path coverage: verifying that all execution paths through a function return a value

Control flow analysis is a prerequisite for more advanced analyses such as data flow analysis and taint analysis.

<?php

function divide(int $a, int $b): float {
    if ($b === 0) {
        throw new InvalidArgumentException('Division by zero');
    }

    return $a / $b;

    // Control flow analysis detects that the line below is unreachable
    echo 'done';
}

?>

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Control Flow Analysis¶

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